1. Field of the Invention:
The present invention relates to an improved hand-held, multidose jet injection apparatus which is particularly suited as a hypodermic jet injector for the injection of medical liquids through the outer skin surface of either humans or animals under sufficiently high pressure to force the liquids to a predetermined depth within the tissues beneath the skin surface. Thus, the apparatus is suitable for the needleless delivery of both subcutaneous and intra-muscular injections.
2. Description of the Prior Art:
Over the past thirty-five years there have been proposed a multitude of hypodermic jet injector devices for the injection of set amounts of medical liquids such a vaccines, medicaments, anesthetics, and the like, without the use of needles. Conventional jet injection devices have a medicament chamber for holding an injectable liquid, a piston for pressurizing the injectable liquid and a nozzle hole or orifice for ejecting the injectable liquid. Such devices have advantages over the classic syringe devices comprised of a syringe cylinder, piston and hypodermic needle in that a needleless jet injection can be effected within a much shorter time and there is no requirement of a newly sterilized needle for every injection.
Only a few of the proposed hypodermic jet injector device designs have been incorporated in commercially available needleless injection apparatus. A needleless injector for diabetics to use for the self-administration of insulin has been marketed by the Derata Corporation under the trademark "Medi-Jector." This hand-held jet injection device is principally designed to deliver subcutaneous insulin injections to a single patient. The device is adjustable as to the volume of medicament delivered and receives the medicament from a vial supported by, and projecting from, the injection delivery end of the device. The power source for ejecting the medicament comprises a number of internal springs which when released (after being compressed) drive a piston which forces the medicament under high pressure through the nozzle at the injection delivery end of the device.
Another hand-held jet injection device for diabetics has been marketed by Mizzy, Inc. under the trademark "SyriJet." A multidose insulin cartridge is side-loaded into the device. Driving power for the medicament is derived from self-contained springs.
There remains a tremendous need for small, portable, hand-held and hand-operated jet injectors which are capable of administering both subcutaneous and intra-muscular multidose injections of a wide variety of medicaments, vaccines, anesthetics and other medical liquids and which can be manipulated under sterile transfer conditions to receive, mix and administer two or more medical liquids as a mixed dose without the entrapment of air.